We examine the effect of weak, small scale magnetic field structure on the rate of reconnection in a strongly magnetized plasma. This affects the rate of reconnection by reducing the transverse scale for reconnection flows, and by allowing many independent flux reconnection events to occur simultaneously. Allowing only for the first effect and using Goldreich and Sridhar’s model of strong turbu...

Magnetic fields are considered to be dominant when εB ≥ εK , being εB = B /8π the magnetic energy density and εK = 1/2ρθ 2 the rotation energy density, for a conventional moderate B= 1 μG. They are considered to be negligible when εB < εK for B ∼ 10μG. With no assumption and no theoretical calculation, we show that magnetic fields cannot be ignored in the outer parts of a galaxy like the Milky ...

We demonstrate that the formation of collapsing cores in subcritical clouds is accelerated by nonlinear flows, by performing three-dimensional non-ideal MHD simulations. An initial random supersonic (and trans-Alfvénic) turbulent-like flow is input into a self-gravitating gas layer that is threaded by a uniform magnetic field (perpendicular to the layer) such that the initial mass-to-flux ratio...

We study numerically the ambipolar diffusion-driven evolution of nonrotating, magnetically subcritical, disk-like molecular clouds, assuming axisymmetry. Previous similar studies have concentrated on the formation of single magnetically supercritical cores at the cloud center, which collapse to form isolated stars. We show that, for a cloud with many Jeans masses and a relatively flat mass dist...

We report the detection of 10 new X-ray filaments using the data from the Chandra X-ray satellite for the inner 6 (∼ 15 parsec) around the Galactic center (GC). All these X-ray filaments are characterized by non-thermal energy spectra, and most of them have point-like features at their heads that point inward. Fitted with the simple absorbed power-law model, the measured X-ray flux from an indi...

In this study, we investigate the shapes of starless and protostellar cores using hydrodynamic, self-gravitating adaptive mesh refinement simulations of turbulent molecular clouds. We simulate observations of these cores in dust emission, including realistic noise and telescope resolution, and compare to the observed core shapes measured in Orion by Nutter & Ward-Thompson (2007). The simulation...

We study energy dissipation and heating by supersonic MHD turbulence in molecular clouds using Athena, a new higher-order Godunov code. We analyze the dependence of the saturation amplitude, energy dissipation characteristics, power spectra, sonic scaling, and indicators of intermittency in the turbulence on factors such as the magnetic field strength, driving scale, energy injection rate, and ...